Monosulphite wood treating process and resulting fiber and paper



crease the production still further.

. neutral,

Patented Nov. 3, 1931 UNITED STATES PATENT OFFICE VIGGO DREWSEN, OF LARGHONT' NEW YORK, ASSIGNOR, BY MESNE ASSIGNMENTS, TO BRADLEY-MCKEEFE CORPORATION, OF. NEW YORK, N. Y., A. CORPORATION OF NEW YORK MONOSULPHITE WOOD TREATING PROCESS AND RESULTING FIBER AND PAPER This invention relates to processes of treating elther deciduous or comferous woods with soluble monosulphite liquor, the monosulphite being used in suflicient quantities to keep the'reaction slightly alkaline throughout the digesting operation, and being substantially .the only digestive reagent employed. It also comprises the peculiar pulp and paper resulting from such a process. This application is a continuation of my previous applications, Serial No. 474,970, filed June 4, 1921, and Serial No. 623,513, filed March 7th, 1923. This invention has been in commercial use by my' authority and under mydirections for sometime, the present daily output of pulp exceeding forty tons, and preparations being under way to in- Monosulphites suitable for the purpose include sodium, potassium and magnesium monosulphites, the first being most conveniently employed. Solutions of all these monosulphites are substantially neutral and are slightly alkaline intheir reaction toward litmus. My process is so conducted that the cooking liquor preserves these substantially slightly alkaline characteristics throughout the digesting operation.

I am aware that various processes involving the use of, more or less soluble monosulphite have been frequently mentioned in I patents and publications for the treatment of vegetable fibers, ever since the publication of the Cross British Patent No. 4,984 of 1880. But so far as I am aware, no commercially valuable process for the treatment of wood by a monosulphite process was ever devised prior to my invention of the process herein described and claimed; I myself succeeded in devising a monosulphite process suitable for't he treatment of cornstalks, bagasse'and other straws, which is described and claimed in my U. S. Patent No. 1,229,422.- But that particular process is not applicable to the treatment of wood without the modifications hereinafter described and claimed. Moreover, the fibers resulting from the treatment of cornstalks, bagasses, etc., as described in my aforesaid patent are of quite different character from those result- Application filed January 29, 1925. Serial No. 5,636.

retained in or converted by the treatment into, a form of cellulose not resulting from the treatment of the same raw materials by other reagents, or by monosulphite used in inadequate quantities.

If the monosulphite be used in inadequate quantities for the treatment of wood, as in the prior processes above referred to, an entirely different series of chemical reactions occurs, the cooking liquor becomes decidedly acid, and the advantages of my process are lost. Again, if substantial quantities of additional reagents such, for example, as caustic soda on the one hand, or sulphurous acid on the other, be employed during the digestion (additional reagents being a feature of most of the processes described in the prior patents and literature above referred to) the reaction partakes of the nature of the usual caustic or bisulphite processes, and the benefits of my invention are not attained. To obtain my results the monosulphite cooking liquor must be used in sufficient quantities and under conditions adapted to produce substantially neutral soluble reaction products with the incrustations of the wood, throughout the digestion.

The use of materially smaller percentages of monosulphite will result in acid reactions, and a much inferior, darker colored, weaker ulp. p For example, I have found that in the case of deciduous'woods it is desirable to use upwards of 33 percent of sodium monosulphite to the air dry weight of the wood treated, and in the case of coniferous woods upwards of 37% of sodium monosulphite. A substantial excess of monosulphite does not interfere with the process, but is of course wasteful. A slight excess of monosulphite over theiminimum proportions is desirable as a safety factor. Other monosulphites may be used in corresponding molecular propor-' tions. In the case of magnesium monosulphite so .large an amount is not soluble in the amount of water it is desirable to employ; but I have found that if the requisite amount be added with the cooking liquor in undissolved form it will react during the digestion and produce the desired results.' It is usually most convenient to use the sodium monosulphite.

Since the cooking liquor remains slightly alkaline throughout my process, it is possible to carry it out in unlined digesters, thus effecting a considerable saving. This cannot be done if smaller quantities of monosulphite be employed because of the acid reaction products formed in such cases.

According to my process the wood chips in the usual form are digested with the monosulphite cooking liquor containing, as

above suggested, suflicient monosulphite to keep the process slightly alkaline throughout the digestion. The concentration of the liquor employed and the time and temperature used in the'digestion may vary widely. The general rule is that stronger concentration and higher temperatures permit of shorter cooking times. In practice it has been found convenient to use a temperature of at least 170 C. and pressure ofv at least 100 lbs., and a concentration, for example, of 110 to 160 grammes of sodium monosulphite per liter of liquor. 1

The time of treatment is usually upwards of ten hours, but of course varies not only with the concentration'and temperature employed, but also with the grade and condition of the wood, the type of .digester used, etc.

The cooked fiber may be washed, separated,

bleached, beaten, etc., in the usual manner.

If, however, it is desired to bleach it, the following process can be conveniently employed with this particular fiber.

Chlorine gas is run into the wet pulp after thorough washing, or alternatively the pulp is treated with chlorine water. A 'tation is advantageously used to promote t e reaction. The chlorine is absorbed by the pulp forming addition roducts without the formation of hydrochloric acid, the bleachimg liquor remaining neutral. In this respect the pulp from my process is peculiar, as other pulps will result in the formation of hydrochloric'acid when treated with free chlorine. The chlorinated products can readily be washed out of my fiber by treatment with hot water. This is another advantage guishing my pulp from others. After washder solution, using for example about 2% on the weight of the pulp .of- 37 percent bleach, will turn the product snow white. The fiber resulting from the use of my process is light colored even before bleaching and snow white after bleaching. Not only 1s the yield of ultimate pure .fiber by my process substantially greater than that obtained from the use of other reagents, but the fiber much stronger and more flexible. It resists the destructive action of the beater more effectively than ordinary wood fiber, and like rag fiber tends when beaten to fray and produce whiskers which materially increase its matting qualities, and the strength and durability of paper made from it. In short, the fiber and paper resulting from my process resemble rag fiber and rag paper more than ordinary wood fiber and wood paper, andare quite superior in appearance, strength and durability to wood fiber and wood paper made by other processes.

It is obvious from the foregoing that many variations may be made in details of the process and product without departing from the spirit and scope of my invention.

What I claim is v 1 1. The process of digesting wood wlth a monosulphite cooking liquor, the monosulphite being used at a sufliciently high temperature and in sufficient quantities in proportion to the amount and character of wood treated to yield a spent liquor which is substantially neutral but alkaline to litmus at the end of the digestion and wood fibers characterized by unusual strength.

2. The process of digesting wood with sodium monosulphite cooking liquor, the sodium monosulphite being used at a sufficiently high temperature and in sufiicient quantities in proportion to the amount and'character of wood'treated to yield a spent liquor which is substantially neutral but alkaline to litmus at the end of digestion'and wood fibers characterized by unusual strength.

3. In the steps comprising digesting wood with a monosulphlte cooking liquor, the monosulphite being used at a sufliciently high temperature and in sufficient quantities in proportion to the amount and character of the process of .making paper the wood treated to yield a spent liquor which is substantially neutral'but alkaline to litmus at the end, of digestion and wood fibers characterized by unusual strength, washing the resultingfibers, and bleaching them by treatment with chlorine. v v

4. In the process of making paper, the steps compi'ismg digesting wood with sodium monosulp to cooking monosulphitebeing used at a suificiently high temperature and' in 'suflicient quantities in proportion to'the amount and character of the to a, spent liquo J lea liquor, the sodium is substantiall neutral but alkaline to lit mus at the en of digestion and wood fibers uantities in proportion to the amount and c aracter of the wood treated to yield 'a spent liquor which is substantially neutral but alkaline to litmus at the end of digestion and wood fibers characterized by unusual stren h, washing the resultin fibers and bleac in them by treatment w1th chlorine, and was ing out the chlorinated products with hot water.

6. As a new product the herein described cellulose fiber produced by the digestion of wood with a monosulphite cooking liquor, the monosulphite present. in'suflicient quantity to yield by reaction with the woody insuflicient quantity to yield cooking of wood'wi M crustations a spent liquor which is substantially neutral but alkaline to litmus at the end of the digestion and such fibers being characterized by unusual strength.

7. As a new product the herein described cellulose fiber produced by the digestion of wood with sodium monosulphite cooking liquor, the sodium monosultphite present in yreaction with the woody incrustations a spent li uor which is substantially neutral'but alka ine to litmus at the end of the digestion and such fibers being characterized by unusual strength.

8. 'As anew. roduct-the herein described cellulose fibers erived from wood but resembling in appearance, strength, flexibility and matting qualities, the-cellulose fibers derived. from rags, such fibers resultin from the pulp having been. subjected to beating to cause fraying of the fibers before the production of plaper therefrom.

13. T e method of producing paper which comprises cooking wood with a monosulphite cookingX liquor to form fibers of unusual strengt and resistance to beating, sub ecting the resulting pulp to a beating operation to cause frayin of the pulp and to increase its matting qua ities and the strength ofthe pa er made therefrom, and forrmng paper of he resulting frayed pulp. I

14. As a new product the paper resulting from the processof the rece g claim.

15. The method of pro ucing aper from short fiber deciduous wood whic comprises cooking the wood with a monosulphite cooking liquor to produce a short fiber Igulp of unusual stren h and resistance to ating, sub'ecting suc pulp to a beating operation su cient to effect fraying of the fibers, and formin paper from t e resulting beatenand frayed bers.

16. As a new product, paper produced in accordance with the claim.

VIGGO DREWSEN.

cooking of wood with-a, monosulp 'ite cooking A liquor. 1

9. As a new product, the herein described strong, flexible, durable reaper composed of wood fibers but resemb g rag paper in finality, such wood fibers being produced by e digestion of wood with a sodium monosulphite cooln'ng liquor. .10. As a new product the herein described gulp made from deciduous short fiber wood y digestion with a monosulphite cooking liquor, such'fibers heir! of unusual strength and being capable of ormin paper of unusual strength without adm xture of long fiber pulp.

11. As a new product, aper made from the pulp of the preceding 12. As a new product, paper frommonosulphite gulp cm; the t a monosulp 'te liquor, the fibers of such pulp having unusual strength and resistance to beating, and such reduced process of the preceding y no 

